Ocular hypotensive agents are useful in the treatment of a number of various ocular hypertensive conditions, such as post-surgical and post-laser trabeculectomy ocular hypertensive episodes, glaucoma, and as presurgical adjuncts.
Glaucoma is a disease of the eye characterized by increased intraocular pressure. On the basis of its etiology, glaucoma has been classified as primary or secondary. For example, primary glaucoma in adults (congenital glaucoma) may be either open-angle or acute or chronic angle-closure. Secondary glaucoma results from pre-existing ocular diseases such as uveitis, intraocular tumor or an enlarged cataract.
The underlying causes of primary glaucoma are not yet known. The increased intraocular tension is due to the obstruction of aqueous humor outflow. In chronic open-angle glaucoma, the anterior chamber and its anatomic structures appear normal, but drainage of the aqueous humor is impeded. In acute or chronic angle-closure glaucoma, the anterior chamber is shallow, the filtration angle is narrowed, and the iris may obstruct the trabecular meshwork at the entrance of the canal of Schlemm. Dilation of the pupil may push the root of the iris forward against the angle, and may produce pupillary block and thus precipitate an acute attack. Eyes with narrow anterior chamber angles are predisposed to acute angle-closure glaucoma attacks of various degrees of severity.
Secondary glaucoma is caused by any interference with the flow of aqueous humor from the posterior chamber into the anterior chamber and subsequently, into the canal of Schlemm. Inflammatory disease of the anterior segment may prevent aqueous escape by causing complete posterior synechia in iris bombe and may plug the drainage channel with exudates. Other common causes are intraocular tumors, enlarged cataracts, central retinal vein occlusion, trauma to the eye, operative procedures and intraocular hemorrhage.
Considering all types together, glaucoma occurs in about 2% of all persons over the age of 40 and may be asymptotic for years before progressing to rapid loss of vision. In cases where surgery is not indicated, topical B-adrenoreceptor antagonists have traditionally been the drugs of choice for treating glaucoma.
Prostagladins were earlier regarded as potent ocular hypertensives; however, evidence accumulated in the last two decades shows that some prostaglandins are highly effective ocular hypotensive agents and are suitable for the long-term medical management of glaucoma. (See, for example, M. S. Starr, Exp. Eye Res. 11, 170-177, (1971); Bito, L. Z. Biological Protection with Prostaglandisn Cohen, M. M., ed., Boca Raton, Fla. CRC Press Inc., 1985, pp. 231-252; and Bito, L. Z., Applied Pharmacology in the Medical Treatment of Glaucomas Drance, S. M. and Neufeld, A. H. eds., New York, Grune & Stratton, 1984, pp. 477-505). There are numerous patent and other disclosures in the prior art describing prostaglandins as ocular hypotensive agents.
In addition to prostaglandins, several other types of chemical compounds are disclosed in the patent and scientific literature as ocular hypotensive agents. For example U.S. Pat. Nos. 5,066,644, 5,091,528, 5,151,440 assigned to the same assignee as the present application, disclose certain oxazoline, thiazoline, imidazoline and 1,4-benzoxazine derivatives as ocular hypotensive agents. An article in Journal of Medicinal Chemistry 1975, Vol. 18, pp 1094-1098 by Bender et al., describe certain heterocyclic homoprostanoids. These compounds, however, are not described to have ocular hypotensive properties.
The presently known ocular hypotensive agents, however, do not cure or alleviate glaucoma and ocular hypertension in a fully satisfactory manner, and/or without undesirable side effects. For this reason, the search continues in the art for further ocular hypotensive agents, particularly for agents which are more effective, have lesser side-effects or act through a different biological mechanism than presently known ocular hypotensives.